The present invention relates to the improvement of a rotary joint of an articulation prosthetic implement having a rotating load setting means, an articulation prosthetic implement using the improved rotary joint, and a method of making (assembling) the articulation prosthetic implement. The present invention is effective as an articulation prosthetic implement for rectification of clubfoot in particular. That is, it can be effectively used for an articulation prosthetic implement configured in that one articulation protecting member out of vertically adjoining articulation protecting members is rotatable against the other articulation protecting member about the axial center in a direction vertical to the adjoining direction.
Clubfoot (talipes equinovarus) is a foot in a state such that the foot turns inward causing the sole to be faced inward, making it unable to control the ankle, and the toe tip side (hereinafter called foot tip) droops downward, and the person is liable to stumble as the foot tip touches the ground in walking, thereby causing hindrance to the walking function.
And, for preventing such stumbling during walking, generally employed is a method that the foot tip is rectified upward in order to prevent the foot tip from drooping downward, and as an articulation prosthetic implement (lower limb implement) to achieve the purpose, various types have been conventionally proposed. As shown in FIG. 7B, a normal state is such that the foot is positioned (shown by solid line) in parallel to the horizontal direction perpendicular to the leg being parallel to the vertical direction, and in that condition, when the foot is moved upward about the ankle bone as shown by imaginary line (chain double-dashed line), it is called back flexion, and when moved downward, it is called bottom flexion.
In the case of a conventional articulation prosthetic implement, for example, it is configured in that a lower articulation protecting member is rotatably connected to a vertically adjoining upper articulation protecting member, and the lower articulation protecting member is rotatable to the back flexion side from the normal state only in a range of a predetermined angle (e.g. 45 deg), and thereby, it is free from bottom flexion from the normal state while being able to make back flexion.
When walking on a flat road by using a conventional articulation prosthetic implement, the normal leg is moved a step forward, and subsequently, the leg on the articulation prosthetic implement is a little inclined forward [see FIG. 8B] just before the leg on the articulation prosthetic implement is moved upward, and as a result, the lower articulation protecting member turning to the back flexion side returns to the normal state due to the foot weight simultaneously when the foot is moved upward, and thereby, it is possible to lessen a chance of stumbling as compared with the case of a foot tip drooping downward.
However, when walking on a downward slope, it is necessary to rotate the articulation protecting member at the foot side (lower side) to the bottom flexion side against the articulation protecting member at the leg side (upper side), but in the above configuration, it is unable to make bottom flexion and the walking is unstable in a bending forward condition, and it is sometimes difficult to make a nearly natural walk. Also, as the foot is placed on the ground when walking on an upward slope, the lower articulation protecting member which supports the foot is able to make back flexion, but when the foot being in a state of bottom flexion is moved up, the lower articulation protecting member returns to the horizontal position due to the foot weight, and it sometimes causes the foot tip to touch the downward slope. By changing the configuration to the one having a rotating angle such that bottom flexion can be made on a downward slope, it is able to walk on a downward slope, but when moving from a downward slope onto a flat road or an upward slope, the configuration is not enough to enable nearly normal walking, and it is very difficult to handle.
In order to solve the above problem, as a prosthetic implement that enables nearly natural walking without limitations on bottom flexion and back flexion, in body prosthetic implements having such a configuration that one body protecting member out of vertically adjoining body protecting members is freely rotatable against the other body protecting member, well-known is the one provided with a rotating load setting means for setting the rotating load to one rotating direction of the freely rotatable body protecting member greater than the rotating load to the other rotating direction (for example, refer to the patent document 1).
[Patent Document 1) International Publication No. 02/39934 Pamphlet (PCT WO02/39934 A1)
However, the rotary section of the prosthetic implement mentioned in the patent document 1 has a cross-section as shown in FIG. 19. That is, circular openings 80K are formed at the lower right and left sides of lower thigh rear plate 80, and inner cylindrical member 86 made of metal (it is preferable to use the one made of synthetic resin or the like if any provided that it has rigidity) which has flange 86A is inserted into one end of the opening 80K from inside, and the flange 86A and lower thigh rear plate 80 are fixed with a plurality of screws B80. Also, circular opening 82K is formed at the upper end of foot bottom plate 82, and outer member 87 made of metal (it is preferable to use the one made of synthetic resin or the like if any provided that it has rigidity) which is externally circular having flange 87A and annular-circular depression 87B is inserted into the opening 82K from inside, and the flange 87A and foot bottom plate 82 are fixed with a plurality of screws B82. And, annular one-way bearing 88 as a rotating load setting means is externally fitted onto circular rotary shaft 87C formed at the center of outer member 87, and the inner cylindrical member 86 is fitted into the remaining space of depression 87B whose space is partially occupied by the one-way bearing 88 externally fitted thereon. Also, stopper 89 which engages projection 87D formed at one end in the axial direction of rotary shaft 87C is fixed on the projection 87D with one screw B83.
Thus, at the rotating section of the conventional prosthetic implement shown in FIG. 19, lower thigh rear plate 80 must be fixed on flange 86A at each end of inner cylindrical member 86 by using screws B80, and it is difficult to perform the torque test of rotary joint (the configuration of FIG. 19 except lower thigh rear plate 80 and foot bottom plate 82).
Also, the rotating load setting means in FIG. 19 comprises outer member 87 internally having a circular depression, inner cylindrical member 86 having a circular projection which engages the outer member, circular one-way bearing 88 inserted into the portion held between the projection and depression of the two members, stopper 89 which engages a disk piece provided at the one-way bearing and the inner cylindrical member, and screw B53 which goes through the screw hole provided in the stopper and the screw hole provided in the outer member. One-way bearing 88 rotates in one direction, but it does not rotate at all in the other direction (opposite direction) even with a force applied, and regarding the configuration of the rotating load setting means, the description is not clear enough to enable the execution of the actual work.